Pneumatic gauge



March 7, 1950 Flled Jan 1, 1945 Patented Mar. 7, 1950 gaat? UNITED STATES PATENT OFFICE PNEUMATIC GAUGE DonatlA. Gauthier,` Detroit, Mich.

Application tianuary 1, 1945, SerialfNo. 570,907'

(Cl. i3- 375) 14 Glaims. l

This invention relates -to gages, and more par.- ticularly to gage apparatus designed for the precise measurement of dimensions;`

The invention relates to that type of gage wherein akjetl terminates in close proximityto the surface to be measured, and a stream of air or other fluid is discharged from the jet against the surface, the distance between the jet and the surface being indicated by a pressure indicating device connectedanterior to the jet;

In my copending application S. N. 541,551, led June 22s, 1944, now abandoned, there is disclosed al gage of the type mentioned, wherein the preslsure indicating apparatus consistsof'a manometer in the form of asimple 1LT-tube.. one leg oi which is open` to atmosphere and calibrated to permit the reading of the height of liquid` within said leg; For purposes of* precise measurement, in units of the order of one-one hundred thousandth of an inch, the manometerl disclosed in said copending application' is not suiliciently ac.- i

curate, because of the iact that evaporation of the liquid or;` other disturbing factorsmay cause fluctuation in the liquid leve-l, and thus cause false readings on the scale. It is also desirable that, for precise` measurement, the pressure of the air orother'iiuidiacting upon the manometer and the jet bemore accurately` controlled.` than isi possible with the apparatus'` disclosed insaid copending application.

The present invention aims to providey a manometer designed to register4 small fluctuations inthe pressure of fluid supplied to. the jet, the heado liquid inthe manometer'b'eing maintained at a constant-value-despitey loss orA dissi'- pationoi the liquid from themanometerdue to evaporation or other causes, or addition theretoV due` to .i condensationv or other causes'. The present invention alsolis designedto supply'air or' other'v iiuidz, to the gage at. more accurately controlled pressure than is possible with-devices of `.the prior art.` en object of' the invention is to provide a pre;- cision gage ofthe typefdescribed, havngigreater accuracy than similar gages ofthe prior art..

A1 further' object of the invention` is,V to` provide a pressure indicating: device; for use; withrsuch gage or.A with other scientifici instruments,

wherein the liquid level-.in the: device isfmaintained: constant:v despiteLloss of; or addition to the liquid through evaporation orl other.:` causes. A." further object of: theiinvention is to provide an apparatusicr registering gaseous-pressures', which apparatus, :shallfhe of.` limproved accuracy andreliabilty. i

A further object of the invention is to provide apparatus for maintaining gaseous pressure in a chamber at accurate and predetermined value.

A` further object of the invention is to provide improved means for maintaining liquid at a constant level'.

A further object ofthe invention is to provide improved apparatus for indicating and` measuring' gaseous pressures, which apparatus shall be of improved construction and design, reliable in operation, and` easily manufactured;

Further objects of the invention will become apparent from the following description, taken in connection with the appended drawings, in which:

Fig. 1 is a View in elevation ofa gage apparatus embodying the present invention;

Fig. 2 is a. View in vertical section of a portion of the' apparatuslshownin Fig. 1; and

Figl 3 isa view in elevation of the apparatus shown in Fig. 1, as viewed from the left thereof.

Before explaining in detail the present inventionwit is to be lunderstood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced orcarried out` in various ways. Also it is to be understood that the phraseology or terminologyI employed` herein is for the purpose oi description andnot of limitation.

The operation ofthe gage disclosed herein dependsuponl the ollowingrprinciple: If a fluid under predetermined pressure is forced` through a conduit having a pair of oriiices` in series with each other, the pressure of the fluid in the conduit `betweenI said orifices will he a function of the relative effective cross sections of the orifices; and if the anterior orifice is of known` and constant cross section, a` measurement of said pressure by means ofainanometer or'the like will indicate the effective cross' section of the posterior oriiice.

The device shown inthe drawings' comprises a gage 'head' of the type disclosed in my copending application abovel identicd, andl mounted in a stationary standard 2li (Fig. 1), which maintainskthe axisoi the head horizontal and spaced from the bench or other support by a sufcient distance to enable work: to be applied thereto conveniently.` The.` work may comprise a machined part having; an internalbore which it is the function of the gage to measure; or may` he any.` spaced parallel. surfaces; The gage head,

shown at the upper left of Fig. 1, comprises a shank 30, of generally cylindrical shape, formed of wearresistant material and having a central longitudinal bore 4i! which communicates by means of a conduit I5 with the pressure regulating apparatus described hereinafter. A nut 34 secures the conduit I5 to the gage head, and a second nut 36 secures the head to the standard 2t. At the rear end of the gage head is a nipple 33 of reduced diameter, which passes through a horizontal aperture in the standard 2li.

The bore communicates adjacent the midsection of the shank with two horizontal cylindrical plugs dit which terminate in oppositely extending jets 46, only one of such plugs and jets being shown in Fig. l. The outer ends of jets lit are ground to define a cylindrical surface which is concentric with the cylindrical outer surface of the shank 30, but of slightly greater diameter. To the rear of the jets 46 a series of hardened inserts 48 are provided at spaced intervals about the circumference of the'head, and forwardly of the jets a similar set of inserts 50 are provided, leaving an interval between the two sets adjacent the jets 46. The inserts 48 and 50 i project outwardly from the cylindrical surface of the shank 30, being secured in longitudinal grooves therein. The outer surfaces of the inserts are ground accurately to define a cylindrical surface of slightly greater dimension than shank 30.

The nose of the gage head comprises a tapered portion 52 at the forward end of the gage head,

vand a cylindrical portion 53, the outer surface of which coincides with the cylinder defined by the inserts 68, 5l). The nose has the function of guiding the gage head into the bore to be measured, and of receiving the blows and shocks which occur when work is carelessly or hastily put upon the gage head, so as to maintain the remainder of the head to accurate dimensions for as long a .time as is possible.

In the operation of the gage head, the piece to be measured, which may be any piece having opposed inner surfaces spaced from each other by a distance slightly exceeding that defined by the inserts 428, 55, is placed upon the gage head. There is thus a slight clearance between the outer surfaces of the inserts 48, 5i) and the surfaces being 'measured while a slightly greater clearance remains between the outer surfaces of the jets 46 and said surfaces. Air or other fluid being supplied to conduit I5 passes to the bore lill and issues at jets @d against the surfaces, forming therewith two circular orifices in parallel with each other. Since the jet outlets lie in close proximity to the surfaces being measured, a circular orice is formed between the two, which restricts the outflow of fluid from the jets to a variable extent dependent upon the distance between the jet outlet and the surface; and since the diametral distance between the opposite jet outlets is known and constant, the restriction to the flow of fluid is a function of the distance between the surfaces being measured, and the back pressure in bore i0 is a function of the distance between said surfaces, so that a nianometer connected to conduit l5 may be calibrated to read directly in linear increments of such diameter. The fluid discharged by the jets 4t flows freely to atmosphere through the spaces between the inserts 48, 58.

Instead of being used to measure the distance between two opposed surfaces, the gage may be used to measure the distance from a predetermined plane. or point to a plane or curved sur- Y it is shown at the right of Fig. 1, and in Figs. 2

and 3. It comprises a base 55 having a removable drain plug 5B therein, and a cylindrical tank 58, which may be of glass or sheet metal or other suitable material. The top of the tank 58 is covered by a metallic cover member 6i), and a removable plug 62 is seated in an aperture in the cover member and provided with vent holes 63 so that the pressure within the tank is at atmospheric at all times. f

Compressed air or other gas, supplied from any source of Ipressure which does not deviate too widely from a predetermined value, is led into the apparatus through an inlet port 64, whence it passes through a cylindrical lter $6 in an annular chamber 5l to the axial bore 68 of a plug 69. Within the bore 68 are seated a series of cupshaped members l0, each of which is formed with an aperture il of such size as to restrict the flow of gas therethrough and damp out any fluctuations which may exist in the gaseous pressure supplied through the inlet port 64, and also to reduce the pressure supplied at the inlet Iport to a lower pressure suited to the smooth operation of the apparatus.

The plug 69 is threaded in a boss 'I2 formed integral with the cover member 60, and terminates in a chamber 13, the pressure in which is to be maintained constant in spite of fluctuations in the pressure supplied through inlet port 65, and in spite of fluctuations in chamber Bt caused by operation of the gage. A pipe 'M extends downwardly from chamber 'I3 in alignment with bore 68 to a point adjacent the bottom of the tank 58. By means hereinafter described, water or other liquid is maintained in the tank 58 at the level indicated by the reference numeral 'I5 in Fig. 2. It will be seen that when air pressure is applied through the port 64, the liquid within the pipe 'I4 will be displaced downwardly and, since the gaseous lpressure is greater than the head of water at the bottom of the pipe, the gas will bubble out of the bottom of the pipe and escape into the space 'l'fY at the upper portion of the tank 58 and thence to the atmosphere through the vent holes 63 or passage H2. The purpose of this arrangement is to permit the escape of excess gas and thus reduce the pressure in chamber 'I3 to that corresponding to the head of liquid indicated at h in Fig. 2. A baie 'I8 is secured to the boss 'I2 and extends horizontally within the space 'I6 to minimize the turbulence caused by the bubbles issuing from the lower end of the pipe 14.

Gas within the chamber I3 may also pass through a conduit 30 in the boss 'I2 to a calibrated restriction 32 formed in a plug 83 threaded into said conduit. Thence it may pass through a chamber 84 to the conduit I5 and thence to the gage head for the purpose above described.

The restriction 82 also communicates with a manometer comprising a glass tube 85 communieating directly with the chamber 84. Its upper, end is seated in an extension 3l of the cover member and is secured therein in gas-tight relation by means of a plug 88. The lower end lof tube 35 is similarly seated in a boss 90 formed in the base of the tank, and is similarly held in place in gas-tight relation by means of a plug 92. The tube thus constitutes `one leg of` a .lmanometeritheotherleg:being thetanicV 5.8;w`zhich v,bis of:` muchi-greaterffcrossasectionaluareathanrthe 1L tubepso .that iiuctuations.in.` theliquicflevel-inithe i tube do :notimateriallyi'affect:theiliquidi-levelain '.Jtheitank. .:-A=shieldrr94,'.Ueshaped inhorilzontal cross section,.;.is;"secured fto @the tank@i 58 l backfof :the'tube1185- ...Fon purpose ofuindicating. the liquid level in 'the tube,jgraduated scales-W6, 91 lare L mounted :within the shieldo94 at opposite sidesifof the tube, @one or both v of `thembeing preferablylf :calibrated to read directly in. linear dimensions lof Ythe measurementfbeing madeat thagag'e head. AWhen so; calibrated,` the `subdivisions-of thescale ware `ofuunequal length, reaching: almaximumlat a point toward the lower portion: oftthe tube, fast` 4.shown .in Eig. i3. .It 'will kbe understood that the apparatus` can with simple changes be adapted .tosu-pply Ligas `to several gage headsea:V separate Lmanometer 1 being used for :each Aof sucnrgage .heads For the purpose of maintaining theliquidlevel within the tank58 at the constant. height. `indi- .cated at l5, inspite of. evaporation'. condensation, :or other factors, there is mountedwthin the tank .58 anv inneritankcindicated generally at |00. .The

.inner-tank has a cover member |02 through which lpasses an annular oricemember |04 the upper .edgeof which `defines or` determinesthe `liquid level 15, and whereby liquidfrom the outer tank may voverflow into the innertank. The inner c.

tank. is also provided with a bottom-member |06 `in which lisumounted oneend ofthelshorter leg |08 `of .a recharging vU-tube, thef other legA |09-` of which extends 4upwardly through .thetank |00 and terminates abovethe cover member |02 ini` the vicinity f itheorifice. member. L04. `.The'` leg |19 passesthrough a horizontalplug ||U positioned beneath'thecover member" |02.-an'd..extend "ing to .the exterior f tank 58.to' serve.as..a support for the inner .tank |00. The plug I0 4is provided with a passage ||2as shownfsothatlit may act' as. anoverow ventfor the tankllll; to ,prei/'entl the liquid level within thetank U'Ulfrom rising above'the line indicated'at |4.

mounted a drainplug i lwhich 'may' be'solo- `cated asito formasupport"forthe tank i110. The plug ||6 is formed'with ahorizontal'ibore at the outer end of which is mounteda cock' I8 "vvhichmayibe manually'` opened by meansof a" handle Sto" drainroutsediment'oifexcess water. The cock l I3 may'alsobe removed "bddilytof permita lexiblewire'to be insertedforcleaning outany cbstru ction in thepassa'ges.

The bore-Hl communicates through an aperfy :bythe une 15. anyadditional.iiquidimrrduced` iigageisthewreadytonoperation.

6 `l-.ffAs losses cof. 'liquidrw-itnflnlthe tank V1158 occur uthroughfevaporationf orfctherwise;thelliquid level H5* tendstoIrdrop,y andato causet falsefreadingssin the manometer H85. This tendency 1 is counter- :f5 acted by the means now to be described.

during fthe i' timei that the gage is I in operation,

gas will iiiowu continuously downwardly through fthe pipei14; issuelaslbubbles" at the bottom ofthe itank, 'land escape 'through the vent holes 63, 4"tliereb-yl maintaining? the pressure l in .chamber 1 3 t @la "value wcorresponding to `the I head of liquid -Lmdicated` at in-Fg-f2. Gas will also flow down- 'lwardlyithroughpipe' |25 andwill issue at'a coniltrolle'd rate llthrough Athe. restricted orifice |24 I to #form bubblesfinthe leg |09 ofkthe `recharging U-tube. The diameter of the U-tube is 'small i'enough vithatthe `Y'bubbles formed 'therein `will fiocculpyithe entire" crossesection of thetube, and ''thetU-tube extendsidownwardly faril enough to #preclude escape of. such bubbles through the `leg M108. The L'bubbles itherefore move upwardly in 2tubel|09an`d `in so doing-pump or move upwardly laheadiiof them increments orslugs of`liquid,"on L'theprinciple ofacoffee percolator, so that the fibubblesescapingattthe upper end of leg H39 force L:lout aheadiofthem aniintermittentdischarge of Iiiquidrwhichliscontinuously withdrawn from the tank l Glandfadded tothe tank-Sato maintain "Ltheiliquid levelltherein fat"tlie constantvalue. Excess liquid discharged into Ftank 58 'by 'this "means, oriorzned therein by condensation of ilatmospheric moistuie;fwill ofcourse overflow the orifice `member lflll and thus return -to thetank 51503 the netfresult i of the l operation will `be` that rany loss of f liquid through. evaporation `or other- "wiseiwll beimadel'goodi fromfthe liquid within tank i100, whilefthe liquid level l5 will remain Iconstant 'The liquid level 'l5 in tank 58 will, wunder certain,`` conditions of temperature and huirni'dity, tend lto' rise due itothe condensaticnof `frnoisturefrom the `air'or other'gas issuing from iapertures'lh yand will cause overflow into tank il Sil' and thence loverflow through passage I I2; `-bi`1't`lunder other conditions the `level ||4 `will `"'gra'duallyl lower-until,` after a' period of perhaps "daysforfweeks, 'itfisfentrely exhausted, `and the level within the recharging U-tube |Q8,|||9 beifcomes so low that compressed gas escaping 'Vthroughftheorifice |24 does not cause liquid to "libe discharged out ofleg |09, but escapes freely 4intofthe -space'll. wWhen thispoint is reached, yany'further loss of lwater 'from tank 58 will not `ibereplenished,"but will cause a drop in the level "i15,\whi`chf will `caus'ethe manometer to read in- 'fcorrectlyy andffwater must again be added to tank F58. The condition ljust describedcan be ascerltainecl'b-y opening-the cock H8, which will apfprise fthe operator'that the lliquid is exhausted lfandnee'dsre1 lenishing.

@Although the `invention has been described with `:particular reference'ito the `illustrated embodi- "ment, itimay-be'embodicd .in other forms and ap.. f plied to many/otheruses. Theapparatus'may Alibe used notonlyforthemeasurement of dimenf'sionsatitheg-age head, but 'is useful independently "'f ythe*"ga`ge Jhead for 'maintaining Aa constant f-liquidlevelfasat l5, and foi-maintaining acon- .s'staznt gaseous'pressure kvas in chamber 13. "It .i-mayi`a1so 'be' used for determining 'or callbrating ftheeiective'crossesection 'of i an voriice' placed in fconduit l5. .Further uses and "adaptations of hefiinventionwill'fsu'ggestSithemselves to itnose filledfiintthe iartif 'smerisuration andifscient'c municating with the rst container.

' be considered as limited to the form disclosed herein, nor otherwise except in accordance with the terms of the appended claims.

I claim:

1. Apparatus for preventing gas pressure in a chamber from exceeding a predetermined maximum, comprising a restricted inlet for admission of gas under pressure to said chamber, a container for liquid, an outlet from said chamber extending to a point below the liquid level in said container, a second container connected to receive liquid from the .rst container when the same reaches a predetermined level, and means utilizing gas under pressure from said chamber to cause` a iiow of liquid from the second container to the iirst container to maintain said liquid level constant.

2. Apparatus for preventing gaseous pressure in a chamber from exceeding a predetermined,l maximum, comprising a restricted inlet for admission of gas under pressure to said chamber,

a restricted outlet from said chamber, a container for liquid, an unrestricted outlet from said chamber extending to a point below the liquid level in said container, a second container connected to receive liquid from the rst container when the same reaches a predetermined level, and means utilizing gas under pressure from said chamber t0 cause return of liquid from the second container to the first container to maintain v said liquid level constant.

3. Apparatus for preventing gaseous pressure in a chamber from exceeding a predetermined maximum, comprising a calibrated inlet to said chamber, a calibrated outlet from said chamber, a container supplied with sealing liquid and open to atmosphere, a second outlet from said chamber extending to a point below the liquid level in said container, a second container within the rst container and connected to receive liquid therefrom when the same reaches a predetermined level in the rst container, and means utilizing gas under pressure to cause return of liquid from the second container to the rst container, said means comprising a U-tube connecti ing the second container to the rst container and a conduit leading from said chamber to said U-tube. f

4. Apparatus for preventing gaseous pressure in a chamber from exceeding a predetermined maximum, comprising a restricted inlet to said chamber, a restricted outlet from said chamber,

a container supplied with sealing liquid, an unrestricted outlet from said chamber extending downwardly to a point below the liquid level in said container, a second container connected to receive liquid from the first container when the same reaches a predetermined level, means utiv lining gas under pressure from said chamber to cause return of liquid from the second container to the rst container to maintain said liquid level constant, and a manometer connected to the gaseous pressure posterior to said outlet and com- 5. Apparatus for preventing gaseous pressure in a chamber from exceeding a predetermined L maximum, comprising a restricted inlet to said chamber, a container supplied with sealing liquid, an outlet from said chamber extending to a point' below the liquid level in said container, a second container connected to receive excess liquid from the nrst container when the same reaches a predetermined level, and means for returning liquid I from the second container to the rst container:

to maintain said liquid level constant,said means comprising a conduit communicating With the lower portion of the second container and with the rst container above said liquid level, and a conduit'ior gaseous pressure leading from said chamber to the lower portion of said rst conduit.

6. Apparatus for preventing gaseous pressure in a chamber for exceeding a predetermined maximum, comprising a restricted inlet to said chamber, a restricted outlet from said chamber, means for indicating the gaseous pressure posterior to said outlet, a container supplied with sealing liquid and open to atmosphere, an unrestricted outlet from said chamber extending to a point below the liquid level in said container, a second container mounted within the first container and connected to receive excess liquid from the first container when the same reaches a predetermined level, and means utilizing the gaseous pressure in said chamber to return liquid from the second container to the first container to maintain said liquid level constant, said means comprising a U-tube having one leg connected to the bottom of the second container and its other leg connected to the rst container and extending to a point above said liquid level, and a restricted conduit leading from said chamber to a point in said U-tube adjacent the bottom of the second container.

'7. The invention defined in claim 6, comprising in addition an overow connection from the second container, a drain cock connected to said U-tube, and said drain cock comprising a removable plug permitting access to said conduit.

8. Apparatus for maintaining constant liquid level, comprising a liquid container having an overilow deiining the maximum liquid level in said container, a second container receiving liquid from said overflow, a conduit leading from the bottom portion of said second container thence downwardly and thence upwardly and terminating at a point above the liquid level in the rst container, and a restricted oriiice for introducing gas from a source under substantially constant pressure in the upwardly extending leg of said conduit at a point adjacent the bottom of the second container to cause flow of liquid upwardly therethrough.

9. Apparatus for maintaining constant liquid level, comprising a liquid container having an overow dening the highest liquid level in the container, a second liquid container receiving liquid from said overflow and having an overilow at a level below that of the rst overflow, a conduit leading from the second container downwardly a sufficient distance to prevent backrlow of bubbles therethrough and thence upwardly and terminating at a point above the liquid level in the irst container, and a restricted orice for introducing gas from a source at substantially constant pressure into the upwardly extending leg of said conduit at a point slightly below the bottom of said second container to transfer liquid from the second container to the rst container.

10. Apparatus for controlling gaseous pressure upon a calibrated orifice, comprising a conduit for gas under pressure connected to said orice,

"a relief outlet connected to said conduit anterior to said orifice, means for maintaininga constant head of liquid at said outlet including a liquid to said orifice and the other leg of which `is formed by said container.

11. Apparatus for controlling gaseous pressure i in a chamber, comprising a restricted inlet to said chamber, a calibrated outlet from said charnber, a container for liquid open to atmosphere, a second outlet from said chamber extending to a point below the normal liquid level in said container, a second container Within the rst container, a connecting orifice permitting overilow from the iirst container to the second container and dening the normal liquid level in the first container, and means utilizing gaseous pressure in said chamber to cause return of liquid from the second container to the rst container, said means comprising a U-tube having its one leg connected adjacent the bottom of the second container and its other leg extending to a point in the rst container above said normal liquid level, and a conduit leading from said chamber to said other leg.

12. Apparatus for controlling gaseous `pressure comprising a chamber, a gas inlet to said chamber, a calibrated outlet from said chamber, a liquid container having an overflow defining the normal liquid level in the container, a second liquid container receiving liquid from said over oW and having an overow at a level below that of the rst overflow, a conduit leading from a point adjacent the bottom of the second container thence downwardly and thence upwardly and terminating at a point above said normal liquid level in the first container, and an orifice in the upwardly extending leg of said conduit connected to said chamber for introducing gas into said leg to transfer liquid from the second container to the nrst container.

13. A pressure regulator comprising a conduit for compressed gas, a plurality of calibrated re strictions in series in said cond-uit, a liquid container having an overflow orice, a gas relief passage leading from a point in said conduit intermediate two of said restrictions to a point in said container below said orice, and a pump supplying liquid to said container and actuated by gas from said conduit intermediate two of said restrictions.

14. A pressure regulator comprising a chamber having a restricted outlet, an inlet conduit for compressed gas connected to said chamber, a liquid `container having an overflow outlet, a relief passage connecting said chamber to said container at a point below the level of said overiiow outlet, a source of liquid, and a pump supplying liquid from said source to said container and actuated by gas supplied by said conduit.

DONAT A. GAUTHIER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,181,726 Bishop May 2, 1916 1,243,604 Honeywell Oct. 16, 1917 1,518,486` Crews Dec. 9, 1924 1,540,684 Eades June 2, 1925 1,982,528 Mennesson 1- Nov.` 27, 1934 2,037,731 Mobley Apr. 21, 1936 2,072,294 Clemons Mar. 2, 1937 2,370,040 Jackson Feb.. 20, 1945 

